Storage battery charge indicator



Feb. 11, 1936. F. J. PEAsE STGR-AGE BATTERY CHARGE INDICATOR Filed Deo.22', 193D I-atented Feb. 11, v1.936 n v l .UNITED STATES PATENT OFFICESTORAGE BATTERY CHARGE INDICATOR Frederick J.' Pease, Wauwatosa, Wis.,assignor to Clum Manufacturing Company, Milwaukee, Wis., a corporationof Wisconsin vApplication December 22, 1930, Serial No. 503,963 3Claims.y (Cl. 13G-182) This invention relates to improvements instorlast mentioned cells as an index showing the ege battery Chargeindicators. The indicator state of charge of the battery as a whole,indeherein disclosed may also be used to detect pendently of otherfactors. A given crosssec-k charges in factors indicative of thecondition of tion of the electrolyte aiords,under stated con- 5 othercells. ditions, a given amount of resistance. By limit- 5 l -It is theprimary purpose of this invention to ing the exposed area of my specialelectrode to Provide a Special eleetrode fOr Storage batteries apredetermined extent, irrespective of changes which may be incorporatedin the closure plug of of level in the electrolyte, I am able to measureone cell of a multi-cell batteryand so connected the resistance of the'electrolyte with laboratory with a special indicating instrument as toshow precision, and to increase the variable portion 1o Vice dOeS netindicate depth'f eleCtl'Olyte at all current and also in resistance ofthe electrolyte 3 the state of charge of said battery through the of thetotal resistance of the circuit to such a use of current developed intheremaining cells. degreeas to give a, wide range of deflection of It isone of the objects of this invention to the indicating instrumentindicativeof the provide an instrument which. because 0f itsCharacteristics of the battery which,fromaprac 15 windings and circuitand the nature of the spetical standpoint, show its useful charge. 15cial electrode used in said circuit, is of suiliciently Whereas ya.specific gravity test will accurately inexpensive and ruggedconstruction to be pracreflect the useful charge of the battery undernorticable in the automotive ileld, While adapted mal summer temperatureconditions, such a test for many other'flelds of use. In carrying outmay'prov'e misleading in cold weather, since the 2;) this Object 0f theinveutin, the use 0f a VOitcold has anA effect equivalent to reducingthe bat- 2o `meter capable of indicating accurately the vatery capacity,I have found, however, that riation in voltage across `the extremeAterminals through the use of the present invention, I obtain of thebattery is avoided because such a meter is at 9,11 Jtimes a. trueindication of the eieotive too expensive and delicate for` the purposesin charge. That is to say, the meter vused in the g5 mind. s circuitherein disclosed will decrease its reading 25 It iS e180 aVelyimpoi'tent Object 0f this i11- in proportion to decreases intemperature, even vention to provide a device which will showacthoughthe specic gravity of the electrolyte recurately the effective state ofcharge of the cell moins constant. Thus, the operator is warned undertest, eliminating, S0 fel aS DOSSible, Such that his battery is becomingless effective at low 3o variable factors as have heretofore beeninvolved temperatures and that to maintain its useful 30 in batterymetersl and are attributable to variacharge heis obliged to increase hischarging rate. i tion indepth of electrolyte, corrosion of the ter-Obviously, this result depends upon the use, as `minals, andvariationsvin the condition of the herein disclosed, of a, circuitaffected largely by plates making' up the bettely- The presentdevariations in the voltage of the cells furnishing l except insofar asit may be rendered inoperative and also upon an electrode so designedthat the when the depth of electrolyte in the cell containarea,exposedto the e1eetro1yte will remain rea..

lmg the Special electlode falls' S0 1 0W that the sonably constantirrespective of changes of level electrolyte does not make contact withsaid elecof the electrolyte.

40 Atroqel More Aspecically stated, therefore, the pur- 40' The device@the present invention'is mended poses of the invention include theprovision of to respond, and does respond, to changes of reaspecial-electrode having a limited of sub sistance both in the cellfurnishing the electroxt t th Envie; f motive force and in the cell inwhich the special manually no vertical e en e pm on o La v Y specialvcircuit including such an electrode and -e1erg$ ai; gs'cndiroved deviceand circuit are enabling it to function in accordance with-the i trpurposes of this invention; the provision of a 50lggdbilggepreo ggg lowresistancemeter which may be supplemented instrument. Its resistance,however, supplements by the resistance 0f the cell 'containing' theSpei) the effect "of voltage variation in the other cells. Cielelectrode; and the DIOViSlOn 0f Special means 50 to contrai thedenection of the instrument. In enabling the device t0 -be used inconnection effect, the resistance of the third cell is used as withexisting motor vehicles aswell as those in a variable multiplyingvoltage external to the which it may be incorporated in factory pro-vcells which furnish energy to the instrument, and duction.

supplementing the internal resistance o f the Other objects will beapparent from the de- 2 2,oso,ee1

.dial I6 is stationary 'and a pointer at I8 moves slstance that theswitch is desirable, so that the circuit is normally open to avoiddraining the scription of the various features of the device and theirfunctions.

In the drawing: Figure 1 is a front elevation of an instrument and amounting bracket therefor, together with a diagrammatic-illustration ofthe circuit in which such instrument is connected.

Figure 2 is a side elevation of the instrument and its mounting,'aportion of the mounting bracket' being broken away to a section exposingits mechanical construction.

Figure 3 is an enlarged detail view in section, of a preferred form,y ofelectrode'to be incorporated in the cell bf Vthe battery which affectsthe meter operation, the relation of the special electrode' to thebattery plates being indicated by a fragmentary illustration of theplates in section.

Figure 4 is a fragmentary detail of a modified form of electrode whichwill also give good results in the circuit shown in Fig. 1.

Like parts are identiiied'by the same reference characters throughoutthe several views.

The application of the indicating instrument to the panel or instrumentboard specially designed therefor, will be a matter of choice, buttoenable the device to be mounted upon an instrument panel 5 which has nospecial provision therefor, there is provided a special bracket 6comprising a cup-shaped member 'I having a central opening through whichthe meter case 8 is receivable- Around the margin of the opening are anumber of centrally inclined yieldable fingers 8 which rigidly engage aninstrument case thrust therein.

The upper part of the cup-shaped member 1 isfformed horizontally, asshown at I II, and is welded or otherwise anchored toa clamp mem-` ber II, one leg of which comprises an ornamental plate I2 for engagement withthe front of the instrument panel 5, and the crher leg I3 of which isinclined toward leg I2 so that the clamp screw I4 will operatedownwardly as well as rearwardly against the panel inengagement with theflange I5 at the 1lower margin thereof.

'I'he instrument preferably includes a dial I 6 having a calibratedsc'ale at I'IA bearing suitable indications as to the relative state ofthe battery. The/extreme ends'of the scale indicative of over or undercharge, are preferably colored 'red. In the particular type ofkinstrument shown, the

across the calibrated scale when it is electromagnetically energized bythe flow of current through the circuit hereinafter to be described. Theinstrument preferably includes a normally open switch, ofwhich thebutton is shown at 28.

'Ihe instrument described is of standard construction with the exceptionof the electrical winding which is preferably designed to afford verylittle resistance as compared with other meters usually employed inbattery testing circuits. It is because of this very low meterrebattery. Itis only by pressing button l2Il, thereby momentarilyclosing the circuit, that the pointer I8 is made to indicate batterycondition. y

The negative terminal of the instrument is connected directly by lead 2Iwith the negative plate 22 of the first battery cell. The second lead 23connects the instrument with the special electrode 24 preferablyincorporated in the last cell of the battery in spaced/relation to theplates thereof. The arrangement is such that the energyv of the cell inwhich electrode 24 is placed does not act upon the instrument.

The special electrode 24 is preferably mounted, or adapted to bemounted,- in a closure cap 25 of a standard storage battery style.without interference with the vent usually provided in such caps. Forthis purpose the electrode 24 may comprises a. rod, screw threaded at28, and pro-l vided with a head'Z'I and a conductorv 28 which ispreferably fused to rod 24, avoiding necessity for the use of corrodableterminals. As a furlther precaution against corrosion, it is preferredIf, as is ordinarily the case, it is undesirable to use the specialelectrode as a means of develop.- ing potential in the cell u nder test,such electrode should be of the1 same composition as the input electrodeof such cell which, in ordinary battery practice, is ninety per centlead and ten per cent antimony. p

Except from the standpoint of convenience, there is no advantage inintroducing the special electrode through the closure cap into the cell,and it will also be obvious that unless the special electrode enters thecell at a point where it passes downwardly across the surface level ofthe electrolyte, there is no advantagel in dielectrically sheathing theelectrode.

The electrode is positioned, as well as insulated, by means of adielectric bushing 35 which covers the whole length of the electrodeexcept the outer face of its headportion 21. The bushing is preferablyrecessed'at 36 to receive the head 21,1eaving only the lower facethereof exposed. The lower face is preferably flush with the end of thebushing, but in order to avoid the possibility of gaseous accumulationson a horizontal surface, the head may be slightly convex as shown inFig.

4, the object being to get it as nearly horizontal l as is practical.

The electrode and its bushing are maintained in the top of the cap.'I'his nut is usedto draw the parts tightly together and thereby toprevent the electrolyte from entering between the electrode and itsinsulating cushion.

Obviously, there would be no difference in principle if, instead ofbeing made of a tube of bakelite or hard rubber, the bushing were castof these materials,` or of glass, or of any other` suitable dielectricand acid-proof material directly upon the electrode. y

The length of the bushing 35 and electrode 24 will be such to maintainthe exposedeface of the electrode in spaced relation to the batteryplates 38, as siown in Fig. 3.

Heretofore the electrodes used in connectionwith battery indicators.havel been exposed throughout their length. To this fact is 'at-f tothe electrolyte should remain as nearly as possible a constant factor.It cannot be constant where the exposed area depends upon the whichpasses through the surface of the electrolyte and disposing the exposedvarea substantially entirely at one level.

The sheathing performs two functions consisting first, in eliminatingthe eiect of change of level of the electrolyte and thereby keepingconstant the exposed area of the special electrode; and secondly, inpredetermining said area. If the electrode does not cross the surface ofthe electrolyte the rst necessity for use of sheathing is eliminated,and the second desirable factor may be achieved otherwise by restrictingthe overall dimension of the portion of the special electrode within thecell.

The voltage of a storage battery is known to vary with the charge. Inthe ordinary battery the variation between full charge and discharge maybe as much as one half volt per cell. In the circuit herein disclosedthere is, therefore, a substantial variation in voltage in the two cellswhich are furnishing the current. As above pointed out, however,laninstrument capable of showing this voltage with reasonable accuracywould have to be a rather delicate and expensive instrument and would,moreover, only *show` the voltage .instead of the effective chargeof thebattery as determined by temperature as well as voltage.

In my improved circuit the reading of the meter is partiallyattributable to the change of volt-1 age in the cells furnishing thecurrent (assuming that the current is derived from one or more cells ofthe battery under test), but a factor in the deflection of the needle ofthe instrument is achieved by reason of the variation of resistance ofthe electrolyte in the cell-which is used as an index to the conditionof the battery by insertion of the special electrode therein.

The exposed area of electrode 2l bears a very important relation to thecharacteristics of the indicating instrument. In order to obtain maximumdeflection the resistance of the instrument and the external circuit inwhich it is incorporated should be low. A meter having a resistance of1.1 ohms has been found satisfactory.

The electrolytic resistance of the cells furnishing the potential wouldof course vary in accordance with the charge of these cells, but thisvariationis negligible because of the enormous area of the plates in theordinary battery. For example, a change in specific gravity from 1.28 to1.1 would increase the resistance of one cubic inch of electrolyte byonly'- one tenth of an ohm. The storage battery is designed to providelarge plate area whereby the variation in resistance is decreased almostto the vanishing point.

The advantage of limiting the area of the special electrode used in theshunt circuit herein disclosed, :s that by means of this limited area`the Aarea for' transmission of current through the electrolyte iscorrespondingly reduced and may,

for example, be of the order of one tenth of a. square inch. With thevariable factor so in creased in resistance, the change of resistancenoted between specific gravities of 1.28 and 1.1 in the electrolyte mayrepresent a change from 1.6 ohms to 2.8 ohms. As compared with the lowmeter resistance of 1.1 ohms, this amount of variation in theelectrolyte resistance is obviously capable of producing a great changein rate of current flow through the circuit, and a correspondingly greatmeter deflection.

In practice the current flowing through the instrument under thecircumstances stated will vary from 1.55 amperes to 2 amperes. in theresistance of the indicating instrument would necessitate acorresponding change in the exposed area of the special electrode. Thus,the special electrode can be used as a means of adapting the circuit tomany desired types and forms of indicating instruments. I

1. An electrolytic resistance test circuit com.- prising the combinationwith a body of electrolyte to be tested, of a source of potential, anindicating instrument comprising a resistance a dial and a pointeraifected by current passing said resistance, an electrode, and a circuitconnecting said electrolyte said source of potential and said instrumenttogether in series, said electrode being immersed in the electrolyteandhaving exposed thereto a surface of predetermined areal substantiallyconstant irrespectivev of normal fluctuation of electrolyte level, saidarea being so small in proportion to the resistance of a unit mass ofelectrolyte, and the resistance of the instrument and the circuit beingso low that the electrolytic resistance of the electrolyte to which saidelectrode area isl exposed is in excess of the resistance of saidinstrument and circuit. v

2. A device ofthe character described comprising a plurality ofelectrolytic cells in series and provided with electrodes, an ammeterprovidejd with a normally open switch. and an auxiliary electrode in a'final cell of said series and of substantially the same material as thenegative electrode of said final cell, each cell of said series otherthan said nal cell being connected in nor mally open circuit throughsaid switch with said ammeter and said auxiliary electrode and theelectrolyte oflsaid final cell, the area of said auxiliary electrodeexposed to the electrolyte of said final cell being substantiallyconstant irrespec-v tive of normal fluctuation of electrolyte level, andso determined with reference to resistance of said amme'ter that theresistance of the electrolyte of the final cell in the circuit exceedsthe resistance of vthe remaining external circuit including the ammeter.

3. A' circuit comprising the electrodes of one battery cell, theelectrolyte ofY a second battery cell, an auxiliary electrode in saidsecond battery cell and a low resistance electromagnetic indicatinginstrument, said electrode having a substantially constant exposed areasuch that the electrical resistance of the electrolyte to which saidarea is exposed is at least as great as that of all of the remainder ofthe circuit includingv the resistance of said instrument.

FREDERICK J. PEASE.

A change.

